


how to build a family

by HeavenlyDusk



Category: Katekyou Hitman Reborn!
Genre: Asexual Aromantic Tsuna, Future Fic, Gen, Other, Queerplatonic Relationships
Language: English
Status: Completed
Published: 2020-03-31
Updated: 2020-03-31
Packaged: 2021-02-28 20:47:37
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,861
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23403226
Author URL: https://archiveofourown.org/users/HeavenlyDusk/pseuds/HeavenlyDusk
Summary: Tsuna and Kyoko become platonic life partners in three parts.
Relationships: Minor or Background Relationship(s), Sasagawa Kyouko & Sawada Tsunayoshi
Comments: 11
Kudos: 337
Collections: Coming Up Aces





	how to build a family

**Author's Note:**

> I wrote this all in one day and I have no regrets. I love making Kyoko and Tsuna be best friends who love each other a whole lot. Also I've been meaning to write ace Tsuna for a while now. I'm quite proud.
> 
> Enjoy!

**1.**

Tsuna and Kyoko become roommates in high school. According to Reborn, the separation from his Guardians is supposed to be a good thing, even though it makes Gokudera cry and Yamamoto’s smile become strained. Tsuna couldn’t help but agree as he tugged his arm from Gokudera’s vice grip, but that still left the problem of who he would live with. Reborn chose a high school away from Namimori—again, claiming that it would be good for him to practice separation from his hometown, as though he didn’t leave every summer and break for Italy anyway—and so he was expected to learn how to manage his own apartment.

Because he and Kyoko were going to the same school, they decided to room together.

(Hana and Haru protested vehemently, for vastly different reasons.

That wasn’t even to mention what everyone else thought, but Tsuna blocked them all out with the ease of someone who had to do so many, many times before.)

They’ve been living together for the majority of their first year by the time they try dating. It seems like the most logical course of action—Tsuna’s infatuation with Kyoko has since turned into real respect and affection, and Kyoko is absolutely certain that she loves the real Tsuna too. It’s hard not to love someone you’ve gone to the future and lived through hell with.

It works out.

Sort of.

They already have an established routine in the apartment. They alternate cooking breakfast and dinner, and they walk to and from school together when neither of them has extracurriculars going on. As roommates, they’ve gone out alone just to hang out when the mood hits them. The only difference from their established routine and their dating routine is that their hang outs become dates and they hold hands sometimes. But, really, it doesn’t feel all that different.

“I guess you’ve practically been dating this whole time!” Yamamoto laughs. Something about it doesn’t sit right with Tsuna, but he shrugs it off. Maybe he’s right. What he has with Kyoko has always been comfortable and he wouldn’t give it up for the world.

The problem starts when they try to kiss.

It’s awkward. The most awkward either of them have been with each other since middle school when Tsuna thought his crush was subtle and Kyoko was trying to let him down easy.

Neither of them can quite manage to hide their expressions from each other.

“We just need to get used to it!” Kyoko says determinedly.

“Right!” Tsuna agrees. They already know they love each other—of _course_ they’ll get used to it.

So they try again the next day.

And again a few days after.

And again the next week, until Kyoko pulls away and yells, “This isn’t working!”

“I’m starting to think I don’t like any aspect of kissing or—anything _else_ , at all,” Tsuna agrees, grimacing.

“Tsu-kun,” Kyoko says fiercely, “I love you, but trying to kiss you feels like trying to kiss my brother.”

“I get what you mean. And, it’s not like we’ve really been doing dating things…”

She nods emphatically. “Right! We’re just doing what we always do. Why did we think this was a good idea?”

“Uhh…” Tsuna tries to think back. Reborn never stopped teasing him about Kyoko, though it did lose its effect soon after the Future. Recently, Yamamoto and Gokudera have been figuring out their feelings for each other and have been telling him about it in _excruciating_ detail—more on Yamamoto’s end than Gokudera’s, and they’re not even together yet. Ryohei, Hibari, _and_ Mukuro all have some weird tension around them too and no one’s really sure what the nature of it is, but it’s disturbing everyone else. Even Haru has put her feelings for Tsuna aside in favor of exploring her own recently-discovered bisexuality.

 _Obviously_ , they both figured, it was time they finally stopped _beating around the bush_. It had been building up since middle school so _of course_ they were going to end up together. Everyone else was thinking about romance (or whatever was up with _those three_ ), so when Kyoko brought it up during dinner one evening, it seemed like the most natural thing to do.

“We’re so dumb!” Kyoko shouts, throwing her hands in the air.

Tsuna moans, dropping his head on the coffee table. “I can’t believe we really spent _weeks_ doing the exact same thing we’ve been doing but worse.”

“Okay, no more trying to date because everyone thinks we should,” Kyoko decides. Tsuna peeks up at her. “We’re definitely going to go insane if we keep trying and I’m not ruining our perfectly good friendship for this.”

“Agreed.” Tsuna sits up straight. “Friends?”

“Best friends!”

They smile widely at each other, and suddenly, everything is as it should be.

When they tell everyone else, Hana practically cries with relief.

(An email shows up in his inbox the next day, with a link to a guide on the aromantic/asexual spectrum. The sender is anonymous, but Tsuna texts Reborn a thank you anyway.)

**2.**

Officially, at nineteen years old, Tsuna hasn’t taken over Vongola yet. He moved to Italy immediately after graduation the year before, and there’s still so much for him to learn about taking over. Unofficially, however, Nono has been giving him more and more work to do, so he’s basically running most of Vongola at this point. Tsuna is convinced that half the reason for this is because Nono is taking the chance to finally be rid of his paperwork.

He and his friends all live together in the main Vongola house. Hibari frequently flies back and forth between Italy and Japan, unable to fully detach himself from Namimori despite his loyalty to Vongola. Mukuro and Chrome are often in-and-out too, casually dismantling small enemies one at a time when they get bored of the mansion. Even the kids came, which was a pleasant surprise as Fuuta cited how he would always follow his big brother. Really, the only ones who hadn’t made a home in the mansion were the girls.

It wasn’t a surprise by any means. All of them stayed in Japan, along with Bianchi and various other teachers to keep them in shape. Haru wanted to pursue fashion before she did anything else with Vongola, and Hana was always too independent to deal with crime before she had her own life and law career together. Kyoko didn’t know what she wanted to do, but she decided to go to college first to figure it out.

The separation was bittersweet, Tsuna thinks wistfully. Over the years, he became used to Kyoko’s steadying presence and to be in a whole other country from her was odd. Other than his Guardians, she was—and still is—his closest friend. He doesn’t fault either of them for it. He can’t get out of the mafia, but Kyoko can, and he has always supported her doing what she can for herself.

A knock sounds on his office door. Tsuna blinks, looking up from his paperwork, and glances at the clock. It’s well past midnight. He didn’t even notice the time passing. There’s an empty plate set aside on his desk, so he apparently ate dinner at some point.

Another knock. He shakes his head. “Uh, yes?” he calls.

“Knock, knock!” sings a feminine voice, and his eyes widen. He would know that voice anywhere.

“ _Kyoko-chan_?”

The door swings open, and there stands Sasagawa Kyoko in all her beautiful, smiling glory. “Tsu-kun! I was very offended when you weren’t there to greet me, you know,” she teases as she enters the room, leaving her suitcase by the door. He stands quickly, almost stumbling in his haste to move around the desk and pull her into a quick, tight hug. She giggles and returns it happily.

“What are you doing here?” he asks as he pulls away. “Is it summer break already?”

“No, not yet. Actually…” She smiles mischievously. “I dropped out.”

“You _what_?” His jaw drops.

Kyoko takes a seat on his couch, comfortable like she’s been here all her life. He sits next to her as she says, “Yeah, it wasn’t really working out. You’ve corrupted me! I couldn’t help thinking about what you guys were all doing without me, and when I tried to join the boxing club, they kept trying to make me their manager.” She rolls her eyes. “Onii-chan could have beaten every single person in that club working together years ago; I had no challenge. And no friends.”

“No friends?” Tsuna asks, though he’s not too surprised. Kyoko has always been kind, but it’s never been to the point where she could easily connect with other people. In a way, it made sense that all her friends were criminals.

“Yeah. Everyone was so _civilian_ , I honestly got bored. As I said, I’ve been corrupted. You made me into a criminal!”

“You didn’t start biting people to death, did you?” he jokes.

“I was tempted to, trust me.”

Tsuna makes a face. “Have you been talking to Hibari-san while I wasn’t paying attention? Don’t do it, Kyoko-chan. It’s not worth it.”

She bursts out laughing and shakes her head. Tsuna can’t help the fond smile that spreads across his face. “Don’t worry, Tsu-kun, I haven’t gone that far off the deep end,” she chuckles. “No, but even being a civilian in Namimori would have been more interesting than that. And, honestly, there was nothing I really thought I wanted to do there, so I dropped out, called Reborn, and now I’m here!” She finishes her explanation with a flourish, spreading her arms out with a wide grin.

“Oh so _Reborn’s_ the reason I haven’t heard about this until now,” he responds dryly, sending her into another fit of giggles. He waits until she’s calmed down to continue, “It’s later than I thought it was, so I can show you to your room, if you’d like.”

“You already have a room set up for me?”

“Of course. We have so many rooms in this place I’m pretty sure we could house a small village, honestly.” He stands, holding out his elbow for her.

She smiles and takes his arm as she stands too. “Sounds fun. Show me to my room, then.”

Tsuna leads her out of his office and heads towards the bedrooms. There’s a room set aside for all of his family, even his mother, unwilling to leave Namimori as she is. When Haru and Hana come to Italy, there’s somewhere for them to stay, too. Technically, Tsuna and his Guardians have their own quarters separate from everyone else—but they all thought that was dumb. Kyoko’s room, just like his mother’s and the other girls and Fuuta and I-Pin’s, is near theirs.

“Here you go,” Tsuna says, presenting the door with _Sasagawa Kyoko_ printed on the plaque in solid letters. Under the Roman alphabet is her name in its normal kanji.

“You really did have a room set up for me,” Kyoko says warmly. She pushes open the door.

Tsuna watches her settle in from the open doorway. The room hasn’t been personalized yet—that’s for her to do in her own time. It still looks like almost every other bedroom in the mansion, but extravagant in a way that makes it different from the regular guest rooms. His family deserved the best, after all.

“By the way,” he says. “I forgot to say it earlier: Welcome home, Kyoko-chan.”

Kyoko looks at him from her place by the bed and smiles. “I’m home, Tsu-kun.”

**3.**

People keep telling Tsuna he needs to get married and have kids.

Actually, they tell him he needs to get married and produce an heir, but even if Tsuna were interested in that kind of thing, he wasn’t interested in having a child just to have them take over. The Vongola inheritance is a dumb tradition anyway and Tsuna has spent the past twelve years chewing Giotto out about it any chance he gets. This would have never been an issue in other Families. Other Families didn’t have to risk literal death by stuck-up ghosts to become boss.

“Kyoko-chan,” Tsuna moans, dropping his head onto her lap. “Everyone is so annoying.”

“Is this about your Guardians again?” she asks sympathetically, like she isn’t just as destructive as they are.

“Not this time, but that’ll probably change by dinner.” He waves a hand. “No, it’s because everyone keeps telling me I need to get married, especially now that Onii-san and Hana are married. I kept getting these _looks_ during the reception, and someone even _casually_ asked what I planned to do for my wedding. Ugh.”

“Not Reborn, I hope? Or your Guardians?”

“No, Reborn thinks I should find Kawahira-san again and make him fix the rings. Our friends just tell me to keep doing what I’m doing and not listen to those old guys.” When the rest of Vongola thinks Tsuna should do one thing, he can always count on those closest to him to have his back. Reborn has taken special glee in being able to shoot people—usually Iemitsu—who think it’s dumb that he does things like skip meetings to celebrate a birthday and reject marriage proposals without meeting or considering the candidates.

Kyoko hums and nods. “Then don’t listen to everyone else. _You_ don’t care about getting married, and none of _us_ care, so what the old guys say doesn’t matter.”

“It kind of does though,” Tsuna admits reluctantly. “I mean, I’m pretty sure most of the reason they think I need to do this is because they still think I’ll get myself killed before my thirties—”

“I’m pretty sure if you tried, you guys could literally take over the world at this point.”

“God, don’t say things like that. But, yeah, they’re all panicking because it’s my late twenties, I’m not married, all my friends are in relationships, blah blah blah, and if I don’t have a kid soon I’ll leave Vongola without an eleventh and all that stuff; and it’s annoying, but they’re right that I need an heir. If it were up to me, I’d adopt, but the inheritance doesn’t work that way and I’m still not entirely sure why the rings are the way that they are. It can’t be easily circumvented.”

Kyoko sighs. “So annoying. Some of the other women have been giving me pitying looks because I’m not married either.”

“That’s dumb.”

“ _So_ dumb.”

The conversation dies for a bit. Kyoko’s fingers run through his hair and he lets himself enjoy it. This is a rare moment for them; though Tsuna refuses to be a workaholic like his father, it does take up a lot of time. The free time he does have, he splits between his Family, but they also have their own work. Kyoko has almost as much work as he and his Guardians—she has the most responsibility as their most trusted confidant who isn’t a former Arcobaleno or a Guardian herself. It’s difficult to find time to be just Tsuna and Kyoko, rather than boss and employee.

“I’ve got it!” she exclaims suddenly, pulling his hair painfully in her excitement. “Oh, sorry, Tsu-kun!”

“It’s fine.” He waves her off, sitting up and rubbing his head where she pulled on him. “What did you figure out?”

“Why don’t _we_ just get married?” she says. “You want kids, I want kids, and we already pretend to be together when it’s convenient. It’s perfect.”

“Uh, one.” He holds up a finger. “We promised to never try dating again. Isn’t this the exact opposite of that? Actually, isn’t this _worse_? Two.” Another finger. “I’m not having sex with you. Three.” A third finger. “What about _your_ dating chances? You can’t date if you’re married.”

Kyoko rolls her eyes playfully. “Getting married doesn’t have to mean being romantic. It’s just some document to get the old guys off our backs. And obviously we won’t have sex; I wouldn’t make you do anything uncomfortable like that. That’s not the only way for me to get pregnant, you know. As for dating…” She shrugs. “It’s not like I’ll ever date outside of Vongola or one of our allies, so whoever I date will know that we’re totally platonic. We can get a divorce whenever we want if it really comes down to it.”

He has no choice but to begrudgingly admit that they’re good points. Kyoko’s too loyal to Vongola, honestly. “Are you sure?” he asks, wanting to make sure she has this all figured out. “This is a _big_ choice, and that’s nine months pregnancy. Nine months doing desk work. Are you sure you want to do this?”

“Do you just not want to get married to me, Tsu-kun?” She pouts.

“Well,” he says, “you never do your laundry, which is terrible because that means _I_ have to get the bloodstains out of your clothes. You put your legs on the coffee table when we watch TV. You’re the _worst_ cuddler ever—”

“I am an amazing cuddler! How dare you!”

“ _Haru_ is an amazing cuddler. _Hayato_ is an amazing cuddler. You never stop moving and what you don’t have in hard muscle is so bony, it’s awful.”

She huffs, turning away from him dramatically. “Well if you hate it that much, we don’t have to get married!”

Tsuna laughs and sets a hand on her shoulder, shaking her lightly. “I’m kidding, I’m kidding. You’re totally right. I just want to make sure you’re prepared for what this means.”

She turns around again to face him fully. “Tsu-kun, you are my best friend. After Hana-chan, of course.”

“Of course.”

“I want a child, and I don’t mind if that child is yours. I don’t mind being pregnant to have that child. I always knew I’d be spending the rest of my life with you, anyway, so this is just another part of that.”

Tsuna takes her hands in his, running his thumb over her knuckles. There’s nothing but utter certainty in her eyes. “Alright. Let’s get married, Kyoko-chan.”

The ceremony, less than a week later, is only them, his Guardians, the kids, Hana, Haru, Enma, and Reborn. Their honeymoon is spent in Namimori.

**Epilogue**

It’s horribly ironic that his father is there when Tsuna’s daughter is born, but he wasn’t there during his son’s own birth.

That’s a bit of a lie. Nana liked to tell the story of how he showed up minutes after Tsuna was born, but for Tsuna’s daughter, he’s been waiting outside the whole time. It makes no sense considering Kyoko refused to have him at their wedding, and he certainly didn’t live in Italy anymore. As soon as he was able to, Tsuna banished his father back to Namimori, to spend time with his wife the way he should have when Tsuna was growing up.

“Come on, she should be able to know her grandpapa!” Iemitsu whines as Tsuna physically hauls him away from the hospital room. If he stayed a minute longer, Kyoko would have handed newly-named Sawada Reina to him and tried to get out of bed to kick his ass. For her own health, Tsuna got them both out of there. She hates Iemitsu about as much as all of his Guardians do. It’s flattering, but ultimately not worth it.

“She needs to know her parents first,” Tsuna says flatly. “You can meet her when Kyoko agrees to have you in the room.”

“Ah, Kyoko. You couldn’t have chosen a better woman,” Iemitsu sighs happily. The man really has no idea how much Kyoko hates him.

“Kyoko’s great,” Tsuna agrees because he’s physically incapable of not praising his best friend and wife.

“You’re just like your old man, eh?” Iemitsu laughs and nudges him with his elbow. “I bet she’s a great cook and amazing around the house, just like Nana!” Tsuna makes a face. Kyoko is wonderful at cooking, but working around the house wasn’t much her thing. Now that she had the freedom to not do housework, her favorite place to be was the gym or on the field. Tsuna was the one who did the housework.

Iemitsu doesn’t notice his expression and finishes up by saying, “I’m sure you’ll have a great love story with this girl! But not as great as me and Nana.”

“What?” Tsuna stares at his father, bewildered. “Me and Kyoko aren’t in love.” It’s not common knowledge for most of Vongola, but his mother knows. As disappointed as she was, she still got a granddaughter out of it and Tsuna was happy, so she was happy all the same.

Iemitsu stares back at him, equally bewildered. “You’re married, son. She just gave birth to your daughter.”

“Yeah, but the marriage was a formality, and so that Reina isn’t seen as a bastard,” Tsuna explains. “We’re just friends.”

“But—you—” Iemitsu stammers. “So you’re not in love?”

“I just said that. I’m not really into that sort of thing.”

“You can’t just _not_ be into _love_ , Tunafish.”

“Stop calling me that.” Tsuna frowns. It’s not that hard to understand. All their friends get it and Reborn was the one who let him know that it was even an option. “It’s not that I’m not into _love_. I love Kyoko and we plan to spend the rest of our lives together; we’re just not romantic.”

Iemitsu stares at him like he can’t possibly comprehend this. Tsuna sighs. Maybe it’s because his father is an empty Sky—he never quite _pulled_ people the way Tsuna has. Not just his Guardians, but all of the close members in the family. They all plan to spend the rest of their lives together, and with Kyoko, it’s a bit different, but still similar. It’s still a close kind of love.

Maybe it’s just that Iemitsu only ever planned to spend his life with Vongola the Famiglia, instead of Vongola the people.

One of the nurses rounds the corner and hurries over, whispering to Tsuna that Kyoko wants him back inside. Tsuna nods and thanks her before turning to his still-confused father. “I have to go back. And you should go back to Mom. You can meet Reina with her.” He turns back to the nurse. She’s a healer first and foremost, but he doesn’t doubt her strength. No one with a brain would dare try to oppose a healer. “Miss, can you please escort my father out?”

“Yes, Decimo,” the nurse says. Tsuna smiles and begins heading back to the room, not bothering any longer with his father.

Kyoko smiles at him as he enters. Reina is in her arms, fast asleep already. “He’s gone?”

“He’s gone,” he confirms, taking a seat at her bedside. He smiles down at his daughter. She’s gorgeous.

Kyoko lets out a tiny huff of amusement. “You want to hold her, Tsu-kun?”

“I would love to.” As gently as possible, he takes Reina into his arms. She barely stirs. Quietly, he murmurs, “Welcome to the world, Reina-chan.” Kyoko leans close to him, head bumping against his as they look at their daughter. He can’t imagine wanting anything other than this.

**Author's Note:**

> Alternate ending of this fic had a pov outsider of a Vongola woman who just climbed up the ranks being like "wow.... decimo has such a gorgeous family...... if his wife were single......." and then Tsuna was like "btw kyoko and i are 100% platonic and you've proven to be pretty trustworthy so do with that what you will"
> 
> Thanks for reading!  
> (psst I'm also on [tumblr](https://heavenly-dusk.tumblr.com/))


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